2. MATERIALS AND METHODS 2.1 Mineralogical Samples & Preparation Materials were sampled and provided to DST by the mining companies involved in the study. A total of two distinct samples. In this study, the following nomenclature is used: 1. EC1 = Enargite flotation concentrate (solids) 2. SB1 = Arsenic-bearing acidic solution from smelter scrubber blowdown. (aqueous) EC1 Sample was thoroughly mixed, dried overnight at 50°C and split using a baffled sample divider to assure representativity; No further grinding was performed. SB1 sample was fully homogeneous upon reception. 2.2 Pyrolysis Test Methodology In a Lindberg tube electric furnace equipped with a 4inches diameter steel tube and dustcollecting filters, pyrolysis tests were performed on the Enargite concentrate (EC1) to remove and capture arsenic as As₂S₃, leaving an arsenic-depleted calcine. Schematic representation of the complete set-up is shown in Figure 1. Tray Electric Lindberg furnace Thermocouple SO2 To ATM Bag filter To on-line gas analyzer Vacuum pump FI Regulator and Flowmeter Screen filter Cooling zone Figure 1 – Pyrolysis work installation with Lindberg furnace and dust-collectors Tests were conducted under SO2 atmosphere on 40g sub-samples at a peak temperature of 650–675°C for 80min, starting when the thermocouple read 600°C. An on-line gas analyzer was linked to the circuit after the furnace to determine oxygen levels post-pyrolysis, indicative of the airtightness of the set-up (<1% for a functioning system). The As₂S₃ by-product collected in the cooling zone and dust filters was oxidated to As2O3, using a similar set-up using a glass tube under air and vacuum. 2.3 Iron-based Arsenic Co-Precipitation Methodology Iron-based co-precipitation was conducted on the scrubber blowdown sample (AS1) to precipitate arsenic as iron-arsenic oxyhydroxide, suitable for vitrification. Tests were performed on sub-samples of 500mL, in a 1L beaker with magnetic stirrer (360 RPM) at room temperature and ambient pressure under a fume hood. A fixed quantity of FeCl3,
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